Shell portability documentation in autoconf manual

[jens . schmidt35]

Hi.

I am referring to the autoconf manual that I found on savannah.org under path 
/autoconf/manual/autoconf-2.63.

Some more issues, continuing the list I started in my previous mail:

Issue 3:
---------

Another reason to be careful with "set -e" on Solaris 10: A failing command 
substitution may not be caught by any means if option "-e" is set. The shell 
bails out immediately:

  $ ( set -e; foo=`false` || echo "foo"; echo "bar" ); echo "baz"
  baz

Issue 4:
---------

Older Bashes (mine is 2.05b.0(1)) may forget exit values if there is a trap on 
exit set and if the trap consists of one succeeding external command only.  
Seems to be fixed in latest Bashes.

  $ /bin/bash -c 'trap "/bin/true" 0; exit 2'; echo $?
  0
  $ /bin/bash -c 'trap ":; /bin/true" 0; exit 2'; echo $?
  2

I hit that problem when I had a "rm -f " clean-up trap in a canned sequence in 
a makefile, where the sequence failed but "make" did not take any notice of 
that fact due to this bug ... not too exotic an use-case, I think.

Regards

Jens

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